I've thought about this a bit more, and I've realised it's not the fetish that's changing. It's actually the same, that one ongoing one. But the other things are more like themes, as they are themes for the obsessions. Not all obsessions become fetishes (or fetish themes) though. There's a few that haven't been. The current one definitely is. And when I'm fantasising, I'm using that object along with the fetish thing.

So I don't have changing fetishes, it's the same one but I get new "themes" from the obsessions. It's still weird but at least I understand that now.